Both, depending on which game you're talking about

difficulty

>>339685370
The hardest game ever XD

Welcome to Dark Souls

game is versatile enough to play however you want

it's popular because things that start out as a challenging can be overcome by simply leveling up and brute forcing it which deludes people into thinking they got better at the game when really all they did was farm

>>339685370
I'd say because it doesn't hold your hand. You have to actually learn from your mistakes, and figure things out for yourself in order to play the game.

The "dark souls is super hard" reputation is more a sign that the current industry has been putting out so many handholdy games to the point that the general gaming community is too used to not having to think of the consequences of death when playing games.

>>339685370
Because they are fun.

I can't speak for others but I got into Souls because of the art direction and because weapons and armor were simple and effective in design which I loved

>>339687861
This. The only reason why people think DS is hard is because it punish you for dying.

>>339685370
Initially it gained a small amount of popularity due to good level design and atmosphere. Many people (casuals) incapable of understanding such things tried the series, but found the games to be "difficult" (it isn't). Since they knew the games were good, didn't know why, and found the games difficult, they assumed that the difficulty was what made the games good. Those casuals far outnumber the people who actually appreciate level design and atmosphere, and further marketing latched onto this demographic. So most fans of the series like it for the "difficulty" but if not for the actual merits in level design and such, the series would not be popular.

It's literally the only RPG with good multiplayer